1. Field of the Invention
The present invention relates to a spinning ring structure for winding a yarn delivered from a yarn delivery unit on a bobbin.
2. Description of the Related Art
A spinning frame employing spinning ring structures of the foregoing kind, and a conventional spinning ring structure will be described. Referring to FIG. 1, a plurality of roving packages 70 are supported on package support bars extending perpendicularly to the sheet of the drawing in an upper portion of a spinning frame. A plurality of drafting units 72 are arranged in rows perpendicular to the sheet of the drawing under the roving packages 70 on the right and the left side of the spinning frame substantially at the middle of the height of the spinning frame. Ring rails 74 are extended perpendicularly to the sheet of the drawing as shown in FIG. 4. The ring rails 74 are supported for vertical reciprocation on vertical ring rail lifting pillars 78 which are driven for vertical movement by a motor, not shown. A plurality of mounting holes 75 (FIG. 4) are formed in a longitudinal arrangement in each ring rail 74 and spinning ring structures 110 are fitted in the mounting holes 75, respectively. Referring again to FIG. 1, a plurality of yarn guides 76 each having a guide hole 77 are supported on vertically movable yarn guide lifting pillars 79 so as to correspond to the spinning ring structures 110, respectively. Separators 95 are disposed between adjacent spinning ring structures 110, respectively, as shown in FIG. 7.
A spindle 80 is supported for spinning so as to extend through and coaxially with the spinning ring structure 10. The spindle 80 is driven for spinning by a motor, not shown. A bobbin 82, not shown in FIG. 1, is put on the spindle 80 and is restrained from turning relative to the spindle 80.
FIG. 14 shows a spinning ring structure 110 as disclosed in, for example, International Publication No. WO96/08592. This prior art spinning ring structure 110 has a stationary ring 20, a rotary ring 30 disposed inside and supported for rotation on the stationary ring 20 and having a flange 32 at its upper end, and a traveler 50 put on the flange 32 of the rotary ring 30 for sliding along the flange 32. A brake ring 160 is disposed under the rotary ring 30. The brake ring 160 is provided on its lower surface with a plurality of radial vanes 168 as shown in FIG. 15.
A roving T.sub.1 unwound from the roving package 70 is drafted by the drafting unit 72 into a fleece, the fleece is twisted into a yarn T.sub.2 as the same advances through the guide hole 77 of the yarn guide 76 and the traveler 50 put on the flange 32 of the rotary ring 30 toward the bobbin 82, and the yarn T.sub.2 is taken up on the bobbin 82 by the agencies of the rotating bobbin 82 (spindle 80), the revolving traveler 50 and the rotation of the rotary ring 30 as the spinning ring structure 110 is vertically reciprocated together with the ring rail 74.
Since the traveler 50 is pressed strongly against the rotary ring 30 by a centrifugal force, the rotary ring 30 always rotates together with the traveler 50 excluding an initial period subsequent to the start of the spinning frame. The brake ring 160 brakes the rotating rotary ring 30 properly to restrain the rotary ring from rotation at an excessively high rotating speed.
A yarn winding speed at which the yarn T.sub. 2 is taken up on the bobbin 82 is equal to a value obtained by subtracting the traveling speed of the traveler 50 on the flange 32 of the rotary ring 30 from the effective circumferential speed of the cop, i.e., the circumferential speed of a portion of a cop built by winding the yarn T.sub.2 on the bobbin 82, in a plane including the yarn T2 being taken up on the bobbin 82. The roving T.sub.1 is fed from the roving 70 at a fixed feed speed. A yarn winding speed at which the yarn T.sub.2 is taken up on the bobbin 82 must be equal to a fleece delivery speed at which the drafting unit 72 delivers the fleece. However, while the spinning ring structure 110 is reciprocated for a cop building operation between a height A and a height B as shown in FIG. 5 and the yarn T.sub.2 is being taken up on the bobbin 82, the diameter d.sub.2 of a portion of the cop corresponding to the height B is large, and the diameter d.sub.1 of a portion of the cop corresponding to the height A is small. Since the angular velocity .omega..sub.0. of the spindle 80, hence that of the bobbin 82, is constant, the circumferential speed v.sub.2 =d.sub.2 .omega..sub.0 /2 of the portion of the cop corresponding to the height B is higher than the circumferential speed v.sub.1 =d.sub.1 .omega..sub.0 /2 of the portion of the cop corresponding to the height A. Accordingly, the traveling speed of the traveler 50, hence the rotating speed of the rotary ring 30, must vary according to the variation of the effective circumferential speed of the cop built on the bobbin 82 as indicated by a curve in FIG. 6 for an ideal mode. However, when the conventional spinning ring 110 is used, the deceleration of the traveling speed of the traveler 50 (the rotational speed of the rotary ring 30) is retarded as indicated by alternate long and two short dashes lines in FIG. 6 in an initial period of upward movement of the spinning ring unit 110 from the height B toward the height A and the actual traveling speed of the traveler 50 exceeds the ideal traveling speed. Consequently, a balloon formed by the yarn T.sub.2 between the guide hole 77 of the yarn guide 76 and the traveler 50 expands or ballooning occurs, and the yarn touches the separator 95 and, in the worst case, breaks, so that the balloon collapses. In FIG. 7, a normal balloon is indicated by alternate long and short dash lines and an expanded balloon is indicated by alternate long and two short dashes lines.
It is inferred from the results of experimental spinning operation that the deceleration of the traveling speed of the traveler 50 is retarded because whirling air currents produced between the cop and the rotary ring 30 by the rotating cop act on the vanes 168 of the brake ring 160 to urge the decelerating rotary ring 30 in its rotating direction.